The invention relates to a method and device for operating a rotary printing press which includes an inking unit having at least one ink distributor roller that oscillates axially with a variable stroke amplitude.
With regard to the method of the invention, it is noted that operating methods have become known heretofore that provide for continued operation of the printing unit without transporting printing material and of the inking unit without feeding and removing ink, whenever interruptions in operation should occur. Lateral distribution is reduced so that in this operating state the ink layer thickness profile, which varies zone by zone in the inking unit, is preserved. Before resumption of the printing mode, predampening of the inking unit is performed. The predampening is necessary so that the ink/dampening medium balance in the inking unit and on the printing form, which was interfered with by dampening-medium evaporation during the interruption, is adjusted immediately to a value favorable for the production run, thereby preventing the development of spoiled copies or waste.
The published European Patent Document EP 0 545 237 B1 describes an inking unit wherein a resumption of a traversing motion of distributor rollers is performed simultaneously with the positioning of ink applicator rollers against a printing form. This can be effected by linking the xe2x80x9cprinting onxe2x80x9d command by circuitry to a tripper device that actuates a switch coupling of the distributor roller, and by linking the tripper device to a pneumatic cylinder that sets the ink applicator rollers into and out of position, respectively. With an inking unit that can be operated in this manner, the ink profile crosswise to the printing direction is able to be maintained considerably longer during the interruption than if there were continued distribution, yet no favorable inking of the printing form is able to be achieved.
The published European Patent Document EP 0 705 692 A1 describes a method and a device for repositioning an inking unit, but they do not overcome the aforementioned inadequacies of the prior art.
With regard to the device according to the invention, it has become known heretofore to use devices for varying lateral-distribution stroke, with which the stroke of a rotating distributor roller can be increased and decreased with the inking unit operating.
In the published German Patent Document DE 36 29 825 A1, a device for axially adjusting the distributor rollers is described, with which the axial motion of the distributor rollers can be regulated from zero to a maximum, and which includes a regulating segment with a drive groove. The regulating segment is rotatably supported on a shaft in a side wall. A device constructed in this manner is technically less complicated to produce, in comparison with the device described in the aforementioned European Patent Document EP 0 545 237 B1, and is less vulnerable to malfunction, because no correctly in-phase latching of coupling parts need be taken into consideration structurally, yet it takes up a great amount of space. Furthermore, an abrupt change between a minimal stroke and a maximal stroke is not possible, because the rotation and locking of the regulating segment with the aid of the gear wheels still takes a relatively long time.
In the German Patent Document DE 25 07 179 C2, a drive for traversing distributor rollers is described that does not overcome the inadequacies of this last-described reference in the prior art.
It is accordingly an object of the invention to provide a method and device for driving a rotary printing press by which the number of spoiled copies resulting from brief interruptions in the operation of the rotary printing press is minimized.
With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, a method for operating a rotary printing press including an inking unit having at least one ink distributor roller that oscillates axially with a variable stroke amplitude, which comprises operating the rotary printing press in a xe2x80x9cprinting interruptionxe2x80x9d operating mode, wherein the ink distributor roller oscillates with minimal stroke, and subsequently operating the rotary printing press in a xe2x80x9cprinting operationxe2x80x9d operating mode, wherein the ink distributor roller oscillates with a normal stroke, and before beginning to operate the rotary printing press in the xe2x80x9cprinting operationxe2x80x9d operating mode, increasing the stroke amplitude of the ink distributor roller.
In accordance with another mode, the method of the invention includes increasing the stroke amplitude from the minimal stroke to the normal stroke.
In accordance with a further mode of the method of the invention, the inking unit has at least one ink applicator roller engageable with and disengageable from a printing form, and the method includes increasing the stroke amplitude when the ink applicator roller is disengaged from the printing form.
In accordance with an added mode of the method of the invention, the inking unit has a plurality of the ink applicator rollers, and the method includes increasing the stroke magnitude when all of the plurality of ink applicator rollers are disengaged from the printing form.
In accordance with an additional mode of the method of the invention, the rotary printing press is a planographic press, and the method includes, before beginning to operate the rotary printing press in the xe2x80x9cprinting operationxe2x80x9d operating mode, predampening the printing unit while thus increasing the stroke amplitude of the ink distributor roller.
In accordance with yet another mode, the method of the invention includes increasing the stroke amplitude to the normal stroke.
In accordance with yet a further mode of the method of the invention, the press is an offset printing press.
In accordance with yet an added mode, the method of the invention includes activating a feeding of dampening medium into the inking unit for the predampening simultaneously with increasing the stroke amplitude of the ink distributor roller.
In accordance with yet an additional mode, the method of the invention includes activating a feeding of dampening medium into the inking unit for the predampening after increasing the stroke amplitude of the ink distributor roller.
In accordance with still another mode of the method of the invention, the planographic press has a dampening unit, and the method includes feeding dampening medium from the dampening unit to the inking unit via at least one roller connecting the inking unit to the dampening unit.
In accordance with still a further mode of the method of the invention, the dampening unit includes at least one dampening medium applicator roller engageable with and disengageable from the printing form, and the method includes predampening the inking unit when the dampening medium applicator roller is disengaged from the printing form.
In accordance with still an added mode of the method of the invention, the minimal stroke is at standstill and has a magnitude of zero.
In accordance with still an additional mode, the method of the invention includes varying the stroke amplitude of the ink distributing roller by triggering a device.
In accordance with another mode, the method of the invention includes triggering the device by an electronic control unit.
In accordance with a further mode of the method of the invention, the device that is triggered for varying the stroke amplitude is an adjustable entrainer having a coulisse and a sliding block.
In accordance with another aspect of the invention, there is provided a device for varying the stroke amplitude of at least one axially oscillating distributor roller in an application unit of a rotary printing press, wherein a distributor roller is drivable by a distributor stroke drive via a distributor stroke transmission including a coulisse having a groove and being adjustable from a first position to a second position, and a sliding block movable in the groove, comprising a first transmission member carrying the coulisse, and a second transmission member carrying the sliding block, the distributor stroke transmission being formed of the first and the second transmission members, the coulisse being disposed adjustably relative to the first transmission member, and both the first and the second transmission members being drivable by the distributor stroke drive.
In accordance with a further feature of the device of the invention, an oscillating driving motion is transmissible from one of the first and the second transmission members to the other of the first and the second transmission members, and the coulisse and the sliding block are cooperable with one another for forming an entrainer.
In accordance with an added feature of the device of the invention, the coulisse in the first position thereof is substantially perpendicular thereto in the second position thereof.
In accordance with an additional feature, the device of the invention includes an actuator for adjusting the coulisse.
In accordance with yet another feature of the device of the invention, the actuator is carried by at least one of the first and the second transmission members.
In accordance with yet a further feature of the device of the invention, the first transmission member is embodied as a lever pivotable about a lever axis.
In accordance with yet an added feature of the invention, the coulisse is rotatable about a coulisse axis, and the groove is formed as a circular arc.
In accordance with yet an additional feature of the invention, the first transmission member is a lever pivotable about a lever axis, and a mean radius of the groove has a length equivalent to a spacing between the lever axis and the coulisse axis.
In accordance with still another feature of the invention, the lever is formed as a multi-armed lever having a lever arm supporting the coulisse.
In accordance with still a further feature of the device of the invention, the lever is constructed for moving at least two distributor rollers opposite to one another.
In accordance with still an added feature, the device of the invention includes an electronic control unit for controlling the actuator to adjust the coulisse.
In accordance with a further aspect of the invention, there is provided a rotary printing press that includes the device for varying the stroke amplitude of at least one axially oscillating distributor roller.
The invention proceeds from the observation that in operating a printing press in a manner heretofore known in the prior art, the adaptation and compensation operations in the inking unit which are necessary to resume the production run and which are performed after resumption of the printing operation mode result in a relatively high rate of spoiled copies. By practising the invention, it has been discovered that spoiled copies can be minimized if the compensation operations are performed during the printing interruption mode and in particular before the ink applicator roller or rollers are brought into engagement with or positioned against the printing form for inking it. By resumption of lateral distribution even before a new onset of printing after an interruption, optimal liquification of the printing ink for inking the printing form is attained by utilizing the thixotropy of the printing ink. Printing is resumed once printing material is again being transported through the printing unit and printed therein, for example, with a command xe2x80x9cprinting onxe2x80x9d fed into an electronic control unit. With this command, in offset rotary printing presses, a stepwise engagement with or positioning of a rubber blanket cylinder first against a printing form cylinder and then against the impression cylinder can be tripped, while in dilithographic rotary printing presses, positioning a printing form cylinder and an impression cylinder against one another, i.e., into mutual engagement, can be tripped. With the command xe2x80x9cprinting offxe2x80x9d, the rubber blanket cylinder can simultaneously be disengaged or positioned away from the printing form cylinder and from the impression cylinder, or the printing form cylinder and the impression cylinder can be disengaged or positioned away from one another.
In the first operating mode, the stroke amplitude of the distributor roller can be increased from a stopped axial stroke or a very short stroke, such as 1 mm. The stroke amplitude can be increased to the normal stroke, which assures favorable lateral distribution during the printing mode, or to an amplitude different from the normal stroke amplitude, i.e., a larger or smaller stroke amplitude. Once the stroke amplitude has been increased in the first operating mode, then a transition to the second operating mode can be effected while continuously preserving this stroke amplitude. However, after an intervening increase, a reduction in the stroke amplitude is also possible, for example, to the minimal stroke, and with the command xe2x80x9cprinting onxe2x80x9d, the stroke amplitude is increased yet again upon resumption of the printing operation mode.
The command xe2x80x9cprinting onxe2x80x9d can preferably also trip a positioning of one or more or preferably all the ink applicator rollers against the printing form to ink it. In this embodiment, the ink applicator roller or rollers are positioned away from the printing form during the first operating mode and positioned against the printing form during the second operating mode. Simultaneously with the onset of inking, a previously interrupted feeding of printing ink from an ink reservoir into the inking unit can be reactivated.
In an especially advantageous feature of the method of the invention, provision may be made for dampening the inking unit during the first operating mode. The dampening medium can be delivered to the inking unit for predampening by a dampening medium delivery device, such as a dampening unit with rollers that is present in the printing press anyway.
Tests have shown that for a comparatively short predampening duration period at increased stroke amplitude, such as over the course of three to four press revolutions, a degradation in zonal ink dosage can be averted to a great extent. The inking unit may be constructed directly dependent upon the type of printing press, and the spacing of the ink distributor roller with variable amplitude from this dampening medium delivery device that supplies the dampening medium can be variable depending upon the press type, such as when there are different numbers of inking unit rollers disposed therebetween. The duration (reaction time) until the dampening medium flows or is fed over the inking roller train until it reaches the ink distributor roller can be correspondingly variable. Depending upon the inertia of the system, the predampening dampening medium can be fed to the inking unit before, after, or preferably simultaneously with the increase in stroke amplitude. An essential feature of this advantageous embodiment of the invention is that dampening medium is fed to the inking unit while the ink distributor roller is oscillating at an increased stroke amplitude, compared to the minimal stroke.
Preferably, a dampening unit that can be operated with a variable supply of dampening medium can be used, and operates in predampening with an increased feed output compared with normal operation. To that end, in a lifter dampening unit, the lifter cycle, and in a film-type dampening unit, the rotary speed of the rollers, such as a dipping roller and a metering roller, can be increased. The duration of predampening and of the lateral distribution with increased stroke amplitude can be referred to a given number of revolutions of the printing unit cylinders (press revolutions) and can be both controlled and variably preselected as a function of other operating parameters of the printing press.
In flat-bed rotary printing presses with an inking unit and a dampening unit, predampening can be performed via at least one roller which at least intermittently connects the inking unit to the dampening unit, and by way of which the dampening medium is fed from the dampening unit into the inking unit, for example, directly onto an ink applicator roller. The predampening of the inking unit can be effected simultaneously with predampening of the printing form, for example, with a dampening medium applicator roller engaging with or positioned against the printing form, and ink applicator rollers positioned away or disengaged from the printing form. This embodiment is advantageous if the printing operation mode is resumed again immediately after the predampening. However, the predampening can also be performed with the ink applicator rollers positioned away or disengaged from the printing form, and the dampening medium applicator roller likewise positioned away or disengaged from it. This variation is advantageous when the onset of printing is delayed after the predampening.
Tests have shown that in predampening in the heretofore conventional manner, that is, with the minimal stroke maintained unchanged, smearlike spots occurred at the onset of printing in the dot-matrix surfaces. These spots result in an additional increase in the number of spoiled copies. The cause thereof was found to be that in conventional predampening with minimal lateral ink distribution, the increasingly fed dampening medium, some of which forms a surface film of water, is smoothened inadequately before it is applied to the printing form and the printing ink located thereon. According to the invention, it was discovered that these printing problems can be averted if the dampening medium fed to the inking unit for predampening during the printing interruption, is distributed together with the ink at an increased stroke amplitude compared with the minimal stroke, that is, with full lateral distribution (normal stroke). As a result, a larger proportion of the dampening medium emulsifies into the ink, and furthermore the remaining film of surface water on the inking rollers is smoothened.
The printing unit, the inking unit and the dampening unit can be controlled by an electronic control unit in a manner adapted to one another. This unit can control the motions of positioning the printing unit cylinders and the ink applicator rollers and the dampening medium applicator roller against and away from the printing form cylinder.
In an especially advantageous mode of the method of the invention, provision may be made for the electronic control unit that controls the printing unit, inking unit and dampening unit also to control the device according to the invention for varying the stroke amplitude, and in particular the actuator thereof.
In the device according to the invention, in particular for performing the method of the invention, namely, for varying the stroke amplitude of at least one axially oscillating distributor roller in an applicator unit, in particular in the inking unit, of a rotary printing press, wherein the distributor roller can be driven by a distributing stroke drive via a distributor stroke transmission which includes a coulisse formed with a groove and adjustable from a first position to a second position, and a sliding block movable in the groove, the coulisse is carried by a first transmission member, and the sliding block is carried by a second transmission member of the distributor stroke transmission, the coulisse disposed adjustably relative to the first transmission member, and both transmission members are drivable by the distributor stroke drive.
With this device, the method of the invention can be performed especially favorably, because the device makes a very rapid change in the stroke amplitude of the distributing roller possible at low adjusting forces brought to bear by the actuator. In contrast with the devices of the aforedescribed prior art, wherein the coulisse guide is used in one case as an adjusting member of a coupling transmission and in another case as a guide cam of a thrust crank transmission, the coulisse guide according to the invention functions as a selectively adjustable entrainer or driver, which in particular can be adjusted from a first position to a second position, and from the second position to the first position. By combining the coulisse with the sliding block, an oscillating driving motion, depending upon whether the coulisse or the transmission member carrying the sliding block is the driving or the driven transmission member, can be transmitted from the first transmission member to the second transmission member, or from the second transmission member to the first transmission member. Disposing the slot on a first movable transmission member and the sliding block on a second movable transmission member of the distributor stroke transmission, and the adjustability of the coulisse relative to the transmission member carrying it, makes it possible, because of a simplified structure of the distributor stroke transmission in particular with respect to the rod linkage, to make better use of the installation space and reduce production costs.
A groove should be understood hereinafter to mean both a groove with a bottom face (base) and an oblong slot without a bottom face, and the term sliding block is understood to mean both a sliding block and a roller. The sliding block may have a circular cross section (such as a bolt) or a polygonal cross section (such as a square).
In an especially advantageous feature of the device according to the invention, provision may be made for the coulisse to be adjustable by an actuator from the first position to the second position; the actuator can be controlled by an electronic control unit, especially by the method of the invention. Electromagnetic actuators as well as pneumatic and hydraulic piston and cylinder units can, for example, be used as the actuator according to the invention. The use of a bidirectional pneumatic cylinder, that is, one that can be acted upon in both directions, is advantageous because with it the coulisse can be retained very securely in the appropriate positions. The method and device of the invention can be employed in sheet-fed and web-fed rotary printing presses.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method and device for operating a rotary printing press, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, wherein: